Not sure of any other way, and I seriously doubt merely using Airtunes in any fashion can do it.
OR at least, since no 'selectable preamp' mode is available
- 7.1 config -> 2 internal amps unused and turned off!
- fronts externally amplified -> preouts used, internal amps turned off!
- Center/SL/SR/SBL/SBR amplified internally -> only 5 internal amps need to be turned on
---> Of course I know I can have a setup that comes very close to this (provided all preouts are live at all times), but the difference is that now all amps will be on all the time.
...and then when I 'migrate' to my new place, the existing 11ch implementation by Denon would fit me perfectly though as I would simply use the 9amps to drive anything but the front speakers and amplify those externally...
- 7.1 config -> 2 internal amps unused
- fronts externally amplified -> an additional 2 internal amps unused
- Center/SL/SR/SBL/SBR amplified internally -> 5 internal amps in use
---> Use the 4 unused amps for Zone2/3. In full preamp mode using Zone2/3 is possible according to the manual by using the front wide and surround back speaker terminals, but that's not what I need since then all other amps are disabled (and I would still not be allowed to choose where I want the Zone2/3 to come out of anyway)... If I interpret the manual correctly, what would be possible though is to have only Zone2 (selectable output from either FH, FW or SB) together with externally amped fronts but then I would still leave 2 amps unused...